Caller ID spoofing has long been the domain of pranksters and scammers, but although the technology often is used unethically, there may be a few legitimate reasons why you would want to disguise your phone number's Caller ID, rather than just block it. Here are a few that come to mind and easy ways to masquerade as someone else.

Some Non-Evil Uses for Caller ID Spoofing

Thanks to the Caller ID Act of 2009, using Caller ID spoofing for causing harm or defrauding someone is a crime. (Telemarketers are also required by the FCC to use an accurate Caller ID number when they call you.)

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Caller ID spoofing in general, however, isn't illegal in the US. There are at least three scenarios where you might want to use it:

Perhaps you're working from home one day but need to place a call to a client or customer and want to appear to be working from the office—or just not give out your home or cell number (Doctors in particular may have this need). With Caller ID spoofing, you can appear to be placing the call from your office.

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Another case scenario is if your friend is ignoring your calls or is simply notoriously hard to get a hold of on the phone, and you really, really need to get through. You should only use Caller ID spoofing in an emergency case, because once your friend answers and finds out you spoofed the Caller ID, it had better be worth it.

Caller ID spoofing is also great for surprising young children: You can place a call as Santa or Cinderella or whoever (many services and apps disguise your voice). This might only work with really young children, however, especially with the limited choices you get for voice disguises.

How to Spoof Your Caller ID

Between 2004 and today, dozens and dozens of Caller ID spoofing companies have been established to meet this incredible need for people to spoof their phone numbers.

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SpoofCard is one of the biggest and oldest, and it offers a free test drive of its service. Enter your number, the number you want to call, and the number you want to be displayed on their website widget to place the call. This is the service I used to place a call supposedly from 867-5309, you know, from Jenny in that song (SpoofCard unfortunately doesn't let you enter in a Caller ID name).

SpoofCard and other services like it work like a calling card, if you've ever used one of those. You dial a number provided to you by the service and then enter an access code or PIN number, plus the recipient's number and your fake caller ID. Also like phone calling cards, you buy credits, starting at $4.95 for 25 credits (1 minute per credit).

My advice, if you're going to do this, is to try out the service first if it offers a free call. I tried out SpoofTel, which offers a free trial and also lets you enter in a display name to be shown in Caller ID, but the call came in as "Unknown" to my phone, which pretty much defeated the purpose. Good thing it wasn't a really critical call I needed to get through to myself.

Lifehacker's Evil Week is all about topics such as password cracking, social hacking and other questionable tricks to make sure you're in the know. Knowledge is power, and whether you use that power for good or evil is in your hands.

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